FISHES. 337 



water, it appears probable, that some warning will be given 

 to the animal of their presence, either by the nerves of the 

 mouth, during the passage of the water to the gills, or by 

 the latter organs. It does not appear, however, that this 

 sense is ever used in the discrimination of food, and does 

 not furnish any characters, for classification, to the ichthyo- 

 logist. 



We have already observed, that the skin of fishes is des- 

 titute of the corpus papillare, and hence anatomists have 

 concluded, that the animals of this class possess the sense 

 OF TOUCH in a very limited degree. Besides, few nerves 

 have hitherto been traced to the skin ; and as its surface is 

 in general coated with scales, it appears but ill adapted for 

 receiving very delicate impressions. In some species, how- 

 ever, such as the common trout, the sense of touch is easily 

 displayed, if, when the fish is resting under a stone or 

 bank, the hand be moved gently towards it, and its sides 

 titillated. It will then exhibit the pleasure it derives, by 

 leaning on the hand, and if the operation be performed 

 with care, every part of the body may be gently stroked, 

 and the fearless fish in part raised above the water. 



Fishes possess no voice by which they can communicate 

 their sensations to others. Some species utter sounds when 

 raised above the water, by expelling the air through the 

 gill opening when the flap is nearly closed : while others, 

 even under water, as the salmon, utter certain sounds while 

 in the act of depositing their spawn ; but for what purpose 

 these sounds are uttered, or by what organs they are pro- 

 duced, we are still ignorant. 



In reference to the Okgans of Nutrition, Fishes ex- 

 hibit innumerable modifications of form and structure. 

 They are all destitute of organs of prehension, and few of 

 them can be considered as furnished with flexible lips. The 

 maxillary structine, hoM'ever, supplies these defects. 



y 



